The invention relates to a device for switching an electrical circuit, in particular for electric power levels of between 500 watts and 10 megawatts. The invention is specifically employed in an electrical infeed from an electrical energy store to the intermediate circuit of an electric drive system in an at least partially electrically-powered vehicle.
Devices of this type are employed for the positive and rapid interruption of high-current electrical circuits in the event of an emergency. A requirement applies to a switching device of this type, in that the tripping and interruption function thereof must be reliably guaranteed, with no maintenance, for a period of up to 20 years. Moreover, a circuit of this type must not give rise to any additional hazard potential associated with hot gas, particles, or an open-circuit voltage which is induced in the circuit in the disconnected state.
A potential field of application in motor vehicle engineering is the positive interruption of on-board cabling from the car battery immediately after an accident, in order to eliminate sources of ignition and plasma interference which occur when, for example, cable insulation has been abraded during an accident, or exposed cable ends are compressed against each other or against sheet metal, and abraded accordingly. If an accident is associated with the simultaneous escape of gasoline, such sources of ignition can ignite combustible mixtures of air and gasoline which accumulate, for example, under the engine hood. A further field of application is the electrical disconnection of a subassembly from the on-board network in the event of a short-circuit in the subassembly concerned, for example, in an electric pre-heater.
Pyrotechnic fuses or disconnecting devices for the switching of high currents are known from the prior art.
DE 44 381 57 C1 relates to a pyrotechnic disconnecting device with a propelling charge, the gases of which act on a working part which is arranged for free longitudinal movement in a housing. The working part stores the energy generated in the propellant gases and, in free-floating motion, acts on the material to be separated. Upon the separation of the material, the working part surrenders its stored energy.
WO 03/067621 A1 relates to an electrical switching device, specifically for the switching of high currents, having a housing, which comprises a contact unit, wherein the contact unit comprises two terminal contacts, which are bonded to the housing in a stationary arrangement or configured as an integral element thereof, for the infeed and outfeed of an electric current to be switched, and wherein the first two terminal contacts, in the initial state of the switching device, are connected within the housing in an electrically conductive manner, having an activatable material arranged in the housing which, further to activation, generates a gas pressure for the pressurization of the contact unit, wherein the electrically conductive connection is interrupted by the action of pressurization associated with the gas pressure, wherein the contact unit comprises a contact element which is moveable relative to the stationary terminal contacts in response to pressurization by the gas pressure generated and which, by the action of pressurization by the gas pressure generated, is moved in the direction of the axis of the contact unit from an initial position to a terminal position, in which the electrical connection via the contact unit is interrupted.
WO 99/54904 relates to a device for the interruption of an electrical circuit, specifically for high current ratings, having a housing, in which at least one electrical conductor element is arranged, which incorporates a separating region and which can be switched into the electrical circuit to be interrupted such that the electrical circuit to be interrupted is routed via the conductor element, and having activatable means which are arranged in or on the housing for the generation of a tripping pressure which acts on the separating region, directly and/or by means of a sabot which pressurizes the separating region in its initial position, wherein the separating region and/or the sabot are configured such that, further to the activation of said means, the separating region is completely interrupted or severed, or the cross section of the separating region is reduced.
DE 44 30 284 B4 relates to a safety device for a motor vehicle, having a disconnecting device which is actuatable by means of at least one accident sensor, by means of which an electrical energy source can be disconnected from an on-board network of the motor vehicle, and having disconnecting means which are subject to the action of propulsive energy, by means of which a conductor in the on-board network can be separated in a manner which interrupts the current flow, wherein, as disconnecting means, a rupture element is provided which is subject to the action of propulsive energy and which functions as a conductor.
If a pyrotechnic disconnecting device according to the prior art is tripped, the interruption of an electrical circuit thus tripped is irreversible under normal circumstances. Thus, in the case of an application in a motor vehicle, the owner of the motor vehicle will generally require the services of a specialized workshop for the replacement of the tripped pyrotechnic disconnecting device. If the interruption of an electrical circuit involves the feeder between the electrical energy store and the intermediate circuit which serves an electric drive system, in general, it will no longer be possible to operate the vehicle by means of the electric drive system.
The object of the invention is the provision of an improved device for the switching of an electrical circuit. Specifically, a further object of the invention is to permit the propulsion of a vehicle using an electric drive system with a tripped pyrotechnic disconnecting device, at least for an interim period.
This object is fulfilled by a device for the switching of an electrical circuit, by a vehicle having such a device, and by a method for operating such a device. Advantageous configurations thereof are described below.
A first aspect of the invention relates to a device for switching an electrical circuit, in particular for electric power levels of between 500 watts and 10 megawatts, which preferably has two or four pyrotechnic disconnecting devices, which are connected in series between a terminal point and a load in order to interrupt the electrical circuit. Moreover, the device preferably comprises at least one closing mechanism, in particular three closing mechanisms, wherein the number of closing mechanisms is also preferably lower than the number of pyrotechnic disconnecting devices, and wherein each closing mechanism is arranged in a parallel connection with, in each case, a single pyrotechnic disconnecting device in order to bridge the one pyrotechnic disconnecting device, and thereby close an interrupted electrical circuit.
A second aspect of the invention relates to a vehicle, specifically an electric or hybrid vehicle, having a device according to the invention for the switching of an electrical circuit, wherein this device is arranged between an electrical energy store and a load, specifically between the electrical energy store and an intermediate circuit.
A third aspect of the invention relates to a method for operating a device according to the invention for switching an electrical circuit, wherein an interruption of the electrical circuit by the tripping of one of the at least two pyrotechnic disconnecting devices in response to a specific event, specifically in an emergency situation, is preferably succeeded by the following steps:                checking whether said specific event has been terminated; and        closing of the at least one closing mechanism which is connected in parallel with the tripped pyrotechnic disconnecting device, in order to bridge the tripped pyrotechnic disconnecting device and thereby close the interrupted electrical circuit; and/or        generation of a status notification for the device, specifically an indication for the attention of the driver of the vehicle.        
The characteristics and advantages of the first aspect of the invention described hereinafter, and advantageous configurations thereof, shall also apply to the second and third aspects of the invention and to advantageous configurations thereof, and vice versa.
The invention is specifically based upon the principle whereby, additionally to a pyrotechnic disconnecting device, a closing mechanism is provided for the closing of a parallel electrical circuit which is arranged in parallel with the pyrotechnic disconnecting device, thereby bridging the tripped pyrotechnic disconnecting device. Accordingly, an electric load, specifically an electric drive system of a vehicle, can be maintained in service, at least for an interim period. This can permit, for example, the vehicle to be driven into an emergency lane or to the nearest repair workshop, or the operation of a service function which is otherwise required further to the tripping of one pyrotechnic disconnecting device to be prolonged until a plurality of pyrotechnic disconnecting devices have been tripped. Preferably, in order to ensure the operational security of the load or of the vehicle in which said load is installed during this time-limited service, the device always incorporates one more pyrotechnic disconnecting device than the number of closing mechanisms which are provided. Accordingly, the affected electrical circuit continues to be protected by a pyrotechnic disconnecting device.
The solution according to the invention firstly enhances the road safety of an electric vehicle, as the latter can continue to operate in an emergency situation and can be driven, for example, out of an exposed position in traffic following an accident. Moreover, by means of the device according to the invention, workshop costs can be saved, for example where the tripping of the pyrotechnic disconnecting device involves an instance of spurious tripping.
In one advantageous configuration, the at least one closing mechanism is a pyrotechnic contactor. Pyrotechnic contactors have a very short response time, and thus permit the rapid closing of an electrical circuit which has been interrupted by the spurious actuation of a pyrotechnic disconnecting device and, accordingly, the prompt resumption of service of the load.
In a further advantageous configuration of the device according to the invention, the at least two pyrotechnic disconnecting devices are in a normally closed state, and the at least one closing mechanism is in a normally open state. A normal state within the meaning of the invention is a state in which the device can be operated in normal duty.
In a further advantageous configuration of the device according to the invention having at least two closing mechanisms and at least three pyrotechnic disconnecting devices, a contact between two respective series-connected pyrotechnic disconnecting devices in a first parallel circuit comprised of a first pyrotechnic disconnector and a first closing mechanism, and a second parallel circuit comprised of a second pyrotechnic disconnector and a second closing mechanism, is commonly employed. This permits an exceptionally space-saving arrangement of the individual elements in the device according to the invention, wherein the individual circuits are employed in a multiple manner.
In an advantageous configuration of the vehicle according to the invention, the terminal point is connected to the negative pole of the electrical energy store.
In an advantageous configuration of the method according to the invention, the interruption of the electrical circuit by the tripping of a further pyrotechnic disconnecting device is preferably succeeded by the following steps:                checking whether the specific event has been terminated; and        closing of at least one further closing mechanism which is connected in a further parallel circuit to the further tripped pyrotechnic disconnecting device, in order to bridge the further tripped pyrotechnic closing device and thereby close the interrupted electrical circuit; and/or        generation of a status notification for the device, specifically an indication for the attention of the driver of the vehicle.        
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.